Cellular phone coverage varies by location and radio access technology. For example, some geographical areas are covered by long term evolution (LTE) radio access technology, some geographical areas are covered by code division multiple access (CDMA) radio access technology, and some geographical areas are covered by LTE, CDMA, and/or other radio access technologies.
Typically, cellular phones are designed to use more than one type of radio access technology and switch between different radio access technologies as needed. For example, a cellular phone capable of using both LTE and CDMA radio access technologies may prioritize the use of LTE, but switch over to CDMA if the LTE signal is weak and the CDMA signal is strong.
Accordingly, when such a cellular phone detects that the signal from its current radio access technology (e.g., LTE) is moderately weak, the cellular phone starts scanning for an alternate radio access technology (e.g., CDMA). If the signal from the current radio access technology (e.g., LTE) continues to be only moderately weak, the cellular phone continues to scan for an alternate radio access technology (e.g., CDMA). Subsequently, if the cellular phone detects that the signal from its current radio access technology (e.g., LTE) is severely weak, and the previously scanned signal from the alternate radio access technology is strong, the cellular phone selects the alternate radio access technology (e.g., switch from LTE to CDMA).
However, scanning for an alternate radio access technology consumes a significant amount of power. As a result, when a cellular phone remains in an area that continues to have a moderate signal level (e.g., LTE is fairly weak, but not weak enough to warrant a switch to CDMA), repetitious scanning for an alternate radio access technology causes a significant degradation in battery life.